FUNDAMENTAL SURVEYING Surveying Equipment & GPS/GNSS 2

Question 1

What is 'DOP' (Dilution of Precision) in GPS surveying?

Accepted Answer

A dimensionless number indicating the geometric strength of the satellite configuration

Answer

DOP values indicate how satellite geometry affects position accuracy — a low PDOP (such as less than 4) means good geometry and better accuracy.

Question 2

Which type of GPS error is largely eliminated by differential techniques (DGPS or RTK)?

Accepted Answer

Common-mode atmospheric errors that affect both base and rover

Answer

Differential GPS cancels errors common to both the base and rover (atmospheric delays, clock biases) as they cancel in the differencing process.

Question 3

What is 'geodetic height' (ellipsoidal height) in GPS terminology?

Accepted Answer

The height above the reference ellipsoid (GRS 80 or WGS 84)

Answer

Geodetic (ellipsoidal) height is the distance above the mathematical reference ellipsoid, not sea level; it must be corrected by the geoid undulation to get orthometric height.

Question 4

What is a 'tribrach' in surveying instrumentation?

Accepted Answer

A leveling base with three foot screws that mounts instruments on a tripod head

Answer

A tribrach is a leveling base with three leveling screws and a forced-centering plate that attaches to a tripod and accepts interchangeable survey instruments.

Question 5

What is 'forced centering' in surveying?

Accepted Answer

A system allowing interchangeable instruments to be swapped onto a tribrach without re-centering over the point

Answer

Forced centering uses matched tribrachs and adapters so that a total station, prism, or target can be interchanged at the same setup point without disturbing the centered, leveled base.

FUNDAMENTAL SURVEYING Practice Test

FUNDAMENTAL SURVEYING Practice Test

FUNDAMENTAL SURVEYING Surveying Equipment & GPS/GNSS 2